There has been proposed a technique of using an electro-oculograph produced by a person's eye movements to identify an area being observed by the person. In this proposal (referred to as proposal 1), electro-oculographic (EGG) electrodes are used to detect the electro-oculograph. Area-of-observation identifiers include a detector which detects the position of the eyes on the basis of the electro-oculograph of the eye movements, and an extractor which, using the detected position of eyes as a reference, extracts from a predetermined area in an image being viewed by the user the area being observed. In proposal 1, while electro-oculography is used to detect the position of eyes, such ocular actions (eye-motion) as vertical and horizontal eye movements, blinking and closing of the eyes, and winking are not distinguishably detected. Thus, such eye movements are not used as data input to a computer.
There has also been proposed a technique of distinguishably detecting various eye movements with an eyewear. In this proposal (referred to as proposal 2), the eyewear takes the form of glasses which include EOG electrodes on the nose pads and the bridge between the lens frames (the part which spans the bridge of the nose) to detect electro-oculographic changes corresponding to the movements of the wearer's eyes. The way in which the electro-oculograph changes depends on the ocular actions (eye-motion) of the wearer (vertical or horizontal movement, blinking, and so on). Using this mechanism, the user can input data corresponding to the variations of eye movements to a computer or the like.
In proposal 2, because the EOG electrodes are provided on the nose pads, the detected electro-oculograph is weak and easily degraded by ambient noise. Therefore, highly accurate detection of eye movement or eye direction becomes difficult to perform based on such a degraded electro-oculograph. If the electro-oculograph becomes stronger, the dynamic range between the noise floor and the peak level of the detected signal increases. In such a wide dynamic range, a plurality of threshold values can be set, and the variety of detection data can be increased by the number of threshold values. In other words, a stronger electro-oculograph is not easily degraded and allows highly accurate detection of various eye movements.
If the electrode arrangement of proposal 1 could be adopted, a stronger electro-oculograph would be detected than is detected in proposal 2. However, the EOG arrangement of proposal 1 is completely different from that of proposal 2 and cannot be simply applied to the nose pads of proposal 2. Therefore, application of the EOG arrangement of proposal 1 (stronger electro-oculograph) to the lens frame of proposal 2 (which can be used in detection of various eye movements) to facilitate the detection performance of the lens frame of proposal 2 is not easily conceivable.